Hadi Moshayedi <hadi@moshayedi.net> writes:
> There is a callback function in fdw's which should also set estimates for
> startup and total costs for each path. Assume a fdw adds only one path
> (e.g. in file_fdw). I am trying to understand what can go wrong if we do a
> bad job in estimating these costs.
> Since we have only one scan path here, it doesn't make a difference in
> choosing the best scan path.
Right. But if there's more than one table in the query, it might make a
difference in terms of what join plan gets chosen. I'd say that getting
an accurate rowcount estimate is usually far more important, though.
regards, tom lane